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Thiyl radical interaction with pyrimidine C5-C6 double bond.
Aleksandra Wójcik1, Sergej Naumov, Bronisław Marciniak
1University of Leipzig, Interdisciplinary Group for Time-Resolved Spectroscopy, Permoserstr. 15, 04303 Leipzig, Germany.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Thiyl radicals interact with pyrimidine C5-C6 double bonds. Pulse radiolysis and quantum calculations reveal addition and elimination rate constants, with addition favored at the C6 position.
Area of Science:
- Chemical Kinetics
- Radiation Chemistry
- Computational Chemistry
Background:
- Pyrimidine derivatives are crucial in biological systems.
- Understanding radical interactions with pyrimidines is vital for drug design and radiation biology.
- Thiyl radicals are reactive species involved in various chemical and biological processes.
Purpose of the Study:
- To investigate the addition and elimination reactions of thiyl radicals with the C5-C6 double bond in pyrimidines.
- To determine the rate constants for these interactions.
- To elucidate the preferred site of radical addition using computational methods.
Main Methods:
- Pulse radiolysis in aqueous solution.
- Utilized p-thiocresol, cysteamine hydrochloride, and mercaptoethanol as thiyl radical sources.
- Applied a modified ACUCHEM computer program for kinetic analysis.
- Performed quantum chemical calculations at the B3LYP/6-31G(d)/PCM level.
Main Results:
- Aliphatic thiyl radicals add to the pyrimidine C5-C6 double bond with rate constants of 1.0-3.0 x 10^7 dm^3 mol^-1 s^-1.
- Elimination of thiyl radicals occurs with rate constants of 0.7-2.0 x 10^5 s^-1.
- Computational studies predict addition at the C6 position with low interaction energy.
Conclusions:
- Thiyl radicals readily add to and eliminate from the pyrimidine C5-C6 double bond.
- The C6 position is the preferred site for thiyl radical addition.
- These findings contribute to understanding pyrimidine radical chemistry and its implications.